This invention relates to an intermittent burning jet engine.
Transient overpressures generated by intermittent and abrupt combustion in a combustor increase the mass averaged exit jet velocity substantially over what could be obtained with steady heat addition with the same inlet conditions and exit static pressure. However, there is a problem in matching intermittent combustions to steady flow upstream components which provide air to the burner.
With instantaneous constant volume combustion, such as occurs in an ideal pulsejet, combustion will cause the pressure to rise in the chamber by a factor of between 4 and 5.
Pressure fluctuations of this magnitude cannot be tolerated in the inlet diffuser of a ramjet engine.
In the present state of the art ramjet inlet diffusers can be designed to withstand pressure fluctuations of approximately 1/100 of this level. If intermittent burning is to be employed in a ramjet engine, some means must be provided for reducing the pressure fluctuations seen by the inlet diffuser, to ensure that the inlet shock wave is not blown out of the inlet diffuser.